Regulating system for low pressure steam generation



Sept. 20, 1932. c. H. SMOOT 1,878,005

REGULATING SYSTEM FOR LOW PRESSURE STEAM GENERATION Filed May 5, 1950 6 INVENTOR 5/ Char/es H. Smear ORNEYS Patented Sept. 20, 1932 CHARLES H. SMOOT, 0F MAPLEWOOD, NEW JERSEY REGULATING SYSTEM FUR LOW PRESSURE STEAM GENERATION Application filed May 8,

The present invention relates to the regulation of the supply of low pressure steam and more particularly to the regulation of the generation of steam for use in chemical processes or the like by control of a reducing valve supplying steam at -an intermediate pressure to an evaporator or the like in which the process steam is generated.

The invention is particularly adapted for use in conjunction with installations of the type wherein a turbine'receiving steam from high pressure boilers exhaust into an evaporator within which process steam is generated and from which the condensate of the turbine exhaust is withdrawn. as feed water for the boilers. When so employed, the invention insures process steam sufiicient to meet the demand therefor when the turbine is not in operation. For an understanding of the invention reference may be had to the accg'mpanying drawing of which:

Fig. 1 illustrates diagrammatically one embodiment of the invention wherein the sole regulation is of a valve in a high pressure bypass about the turbine, and

Fig. 2 illustrates in perspective an embodiment of the invention generally similar to that of Fig. 1 but wherein dampers or valves in the process steam lines are controlled in addition to the control of the valve in the high pressure by-pass about the turbine.

Referring first to Fig. 1 a turbine l, driving the generator2, receives steam from a high pressure main 3 and exhausts into a pipe 4 leading'to an evaporator 5 of any suitable construction. Raw make up Water is supplied to the evaporator 5 through a pipe 6 and the process steam generated in the evaporator is withdrawn; therefrom through the pipe 7. The condensate from the exhaust steam is withdrawn from the evaporator through the pipe 8 from which it may be delivered to points of use, as, for example the feed-Water pumps of boilers supplying steam to the conduit 3. To insure a sufiicient supply of process steam when the turbine is idle a by-pass 9 is provided about turbine 1 in which by-pass is a valve 10. When the turbine is out of operation valve 10 is controlled to maintain normally a cpnstant 1930. Serial No. 449,671.

pressure in steam pipe 4 but to vary this pressure upon variation in the demand for process steam as measured by the pressure in pipe 7. A regulator 11 controls the position of valve 10 through the intermediary of a pilot valve 12 and relay cylinder 13.

The steam of valve 10 is connected to the piston of relay 13 which in turn, by means of a rod 13 is linked to a floating lever 14 to which the piston of pilot valve 12 and a rod 15 are also linked. Rod 15 is connected to the pivoted power arm 16 of the regulator 11. The arrangement is such that a counter clockwise movement of arm 16 about its fixed pivot point 16 raises rod 15, causing rocking of lever 14 about its connection with the rod 13 and a consequent opening of pilot valve 12 in a direction to connect the fluid supply pipe 57 with the upper part of cylinder 13 and'the fluid exhaust pipe 58 with the lower part of the cylinder. The downward movement of the piston of relay cylinder 13 thus occasioned by the opening of the pilot valve partially closes valve 10 and at the same time closes the pilot valve by means of lever 14. Conversely a clockwise movement of power arm 16 about its pivot 16 causes operation of the pilot valve to cause opening of valve 10; the pilot valve being simultaneously closed by the upward movement of rod 13.

Regulator 11 is preferably of the balanced type and may comprise any suitable means for causing operation of power arm 16 upon departure of the pressure ofthe steam in pipes 4. from the desire value and in response to a function of the demand for process steam.

In the particular construction illustrated in the drawing regulator 11 comprises a pivoted balance lever 17 adapted upon displacement from neutral position to vary the position of a throttle valve 18 controlling the leakage of actuating pressure fluid from a chamber 19. A piston 20, provided with a restricted pressure equalizing passage therethrough and movable in response to pressure changes in chamber 19 carries a rod 21 to which is linked one end of the pivoted arm 16. A rod 22 connected at one end to lever 17 and at its other end to a diaphragm 23 forming a movconnected to the able wall of a chamber 24 transmits to the lever a force varying with the pressure in chamber 24 and with the compression of a compression spring 25 connected between a fixed part of the regulator and the diaphragm 23. Chamber 24 is connected to pipe 4 by means of a pipe 26. Opposing the force on lever 17 due to the pressure in chamber 24 is a controlling force due to the tension of a spring 27 connected to the other end of lever 17 and to a rack 28 slidably mounted in a fixed guide 29 and vertically movable therein by means of a pinion 30. A reversible electric motor 31 through suitable reduction gearing drives pinion 30 in one direction or the other under control of a regulator 32 responsive to the pressure in conduit 7.

Regulator 32, as diagrammatically illustrated, comprises a pivoted balance lever 33 acted upon in one direction by the pressure in pipe 7 as transmitted to a diaphragm closed chamber 34 and in the other direction by a controlling force due to spring 35 the tension of which is varied by a reversible electric motor 36 associated therewith and energized in one direction or the other when lever 33 departs from neutral position. Motors 31 and 36 are connected in parallel to a suitable source of electro-motive force indicated diagrammatically by the terminals 37, one terminal of which is connected to one terminal of each motor and the other terminal of which is connected to a contact 38 carried by lever 33; fixed contacts 39 and 40 located above and below lever 33 respectively in positions to be engaged by contact 38 upon departure of the balance from neutral being other two terminals of motors 31 and 36.

To prevent over-travel and consequent hunting of regulator 11 a dash-pot 41 is carried by the rod 21 and a piston 42 slidable therein iscarried by lever 17. This arrangement adds a temporary force to the balance during movement of the power piston tending to restore equilibrium upon the balance in advance of the return of the pressure in chamber 24 to its desired value.

When the turbine 1 is operating and supplying suflicient exhaust steam the outer end of power arm 16 of regulator 11 is manually clamped in its lowermost position by means of a bolt 43 and the supply of pressure fluid to the regulator is shut off by means of a valve 44 in the fluid supply pipe 45 to maintain valve 10 in closed position. When the turbine is not in use, or not supplying sulficient exhaust steam, lever 16 is manually released and valve 44 is opened, whereupon regulator 11 is put into operation to contro valve 10. With the automatic regulation thus in operation, if there is. a steady demand for process steam and a. steady pressure in main 3, valve 10 will be at some intermediate position and the balance levers 17 and 33 of 1 trated in Fig. 1, the

regulators 11 and 32 will be in equilibrium. If now, for any reason, the pressure in the steam main falls, then the pressure in con duit 4 will fall and this in time would result in insuflicient generation of steam in evaporator 5 if valve 10 were not controlled to correct for this drop in pressure. Before the reduction in pressure has appreciably eilected the process steam generation, however, the reduction of pressure in chamber 24 of regulator 11 causes an unbalance of the forces upon lever 17 in a direction to lower valve 18 and to thereby increase the pressure in chamber 19. Piston 20 is thereupon raised due to the unbalance of pressures thereupon and arm 16 is tipped in a direction to cause the piston of pilot valve 12 to be lowered and to thereby supply fluid below the piston in relay cylinder 13. Relay 13 will thereupon open valve 10 and simultaneously, through lever 14, close the pilot valve. If the opening of valve 10 has increased the pressure in pipe 4 sufiiciently to restore equilibrium upon lever 17, no further movement of valve 10 will be efiected. If the pressure in pipe 4 is still too low, regulator 11 will again operate to further open valve 10 until the desired pressure is restored. If the demand for process steam should increase, the pressure in pipe 7 will drop, causing unbalance of lever 33 and closure of contacts 38 and 40 to energize motors 31 and 36. Motor 31 will thereupon be operated in a direction to increase the tension of spring 27 and motor 36 will be operated in a direction to decrease the tension of spring 35 to thereby restore equilibrium upon lever 33 and to open the circuits of the motors when the tension of spring 35 is such as to balance the pressure in chamber 34. The increased tension of spring 27 occasioned by the above energization of motor 31 causes operation of regulator 11 in a direction to open valve 10 until the pressure in pipe 4 increases sufliciently to restore balance upon lever 17. Regulator 11 will then continue to maintain this increased pressure in pipe 4 so long as the demand for process steam continues at the same value. A chan e in the demand for steam thusoperates t rough regulator 32 to readjust the value to which the pressure in pipe 4 is maintained by regulator 11.

When .it is desired to have a' more rapid response to changes in demand for processsteam, and where the evaporator is so constructed asv to be able to withstand relatively higher pressures than those to which it would be subjected in the arrangement illusarrangement disclosed in Fig. 2 may be advantageously employed. In Fig. 2 those elements which may be identical with ones already described are indicated by the same reference numerals as in Fig. 1. Most of that part of the disclosure which is common to the two embodiments has been omitted from Fig 2 for simplicity. Referring to Fig. 2 the pipes 7 and 7 leading from the evaporator 5 are provided with dampers 46 and 46 adapted to be conjointly operated upon rotation of a rod 47. Rod 47 is mountedin suitable bearings 48 and carries a pinion 49 meshing with a rack 50 linked to the power arm of regulator 51. Movement of rod 47 through a pinion 52 is arranged to vary the tension of spring 27 of regulator 11 thus replacing the motor 31 of Fig. 1. Regulator 51 is responsive to the demand for process steam as measured by the pressure in pipes 7 and 7 and transmitted to the diaphragm closed chamber 53 by means of pipes 54. The construction of regulator 51 may be essentially alike that of regulator 11 except that stabilizing springs 55 are connected between the movable members of the dash-pot 56 to insure a definite position of the power arm for each pressure'in chamber 53.

With the arrangement illustrated in Fig.

. 2 an increase in demand for process steam causes operation of regulator 51 in a direction to open valves 46 and 46 and to thereby reduce the pressure in evaporator 5, which thereupon generates additional steam to meet the demand therefor. Simultaneously with the opening of valves 46 and 46 the rotation of rod 47 increases the tensionof spring 27 to cause unbalance of regulator 11 and consequent operation in a direction to open valve 10 and to thereafter maintain a higher pressure in pipe 4. Conversely a decreasein the demand for process steam causes operation of regulator 51 to close valves 46 and 46 and'to cause operation of regulator 11 in a direction to maintain a lower pressure in line 4. Variations in the pressure of the high pressure steam, as measured in chamber 24, react upon regulator 11 in exactly the same manner as already described in connecton with Fig. 1.

Two embodiments of the invention have now been described. in each, a regulator responsive to a controlling force (specifically the tension of spring 27) and to the pressure of the steam delivered to an evaporator, is provided for normally maintaining this pressure constant, and in each additional means responsive to the demand for low pressure steam is provided for adjustment of the controlling force acting upon the regulator to vary thereby the controlled pressure with the demand for low pressure steam. In one embodiment additional means are provided for directly varying the supply of low pressure process steam by calling upon the accumulator capacity of the evaporator. By the provision of one or more regulators responsive both to the pressure of the steam delivered to an evaporator and to the pressure of the steam generated therein, or to any other force varying as a function of the demand for such steam, the delay which would necessarily result from a regulation solely in response to one or the other of the above pressures is eliminated and more ellicient operation of the evaporator is insured.

The following is claimed:

1. In combination with an evaporator receiving steam at one pressure and generating steam at a lower pressure from water delivered thereto a regulator responsive to the pressure of the steam delivered to the evaporator and to a controlling force, and adapted to so control the pressure of the steam delivered to the evaporator as to maintain it in proportion to said force, and a second regulator responsive to a force varying with the demand for the low pressure steam generated in said evaporator and adapted to vary the controlling force on said first mentioned regulator in a direction to cause the pressure of the steam delivered to the evaporator to increase when the demand for low pressure steam increases.

2. The combination according to claim 1 wherein said second regulator is not only adapted to vary the controlling force on said first regulator but also is adapted to directly vary the pressure within said evaporator.

3. In combination with an evaporator receiving exhaust steam from a turbine and generating low pressure steam from water supplied thereto, a turbine, a regulating system comprising a valve in a by-pass about said turbine a regulator for said valve responsive to the pressure of the steam supplied to the evaporator and to av force varying as a function of the demand for the steam generated therein, and means associated with said re ulator for closing off said valve when desired.

4. In combination with an evaporator receiving steam at reduced pressure from a high pressure steam main and generating low pressure steam from water supplied thereto, a valve between the high pressure main and the evaporator for reducing the pressure of the steam delivered thereto, and a regulator for said valve adapted to vary the pressure of the steam delivered to said evaporator in response to the demand for the low pressure steam generated therein.

- 5. The combination according to claim 4 including means responsive to the demand for low pressure steam generated in the evaporator for directly varying the pressure within said evaporator.

6. In combination with an evaporator adapted to receive steam from a high pressure steam main and to generate low pressure steam therein, a device for reducing the pressure of the steam delivered to said evaporator, a balance mechanism subjected to a force varying with the pressure of the steam at the low pressure side of said device and to a force varying with the demand for steam generated in said evaporator, and means brought into operation upon departure of said balance mechanism from equilibrium for adjusting said device until said balance mechanism is in equilibrium under the forces acting thereupon.

7 A system for generating low pressure steam and for regulating the generation of the steam comprising in combination a high pressure steam main, an evaporator connected by a pipe to said main, a valve in said pipe, a conduit for conveying low pressure steam generated in said evaporator to points of use, a regulator for said valve adapted to maintain the pressure of the steam in said pipe on the low pressure side of said valve in definite relation with a controlling force acting upon said regulator, and a second regulator adapted to maintain the controlling force on said first regulator in definite relation with the pressure of the steam in said conduit.

8. The combination according to claim 7 wherein said conduit for conveying away the low pressure steam generated in said evaporator is provided with a throttling device, and wherein said second regulator controls said device and varies said controlling force upon said first regulator in response to the pressure beyond said device whereby the accumulator action of said evaporator is utilized to vary the supply of steam in said conduit in rapld response to changes in the demand therefor.

In testimony whereof, I have signed my nameto this specification.

CHARLES, H. SMOOT.

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